The Collaborative International Dictionary of English v.0.48:

Bisexual \Bi*sex"u*al\, a. [Pref. bi- + sexual.] (Biol.)
   Of both sexes; hermaphrodite; as a flower with stamens and
   pistil, or an animal having ovaries and testes.
   [1913 Webster]

WordNet (r) 3.0 (2006):

bisexual
    adj 1: sexually attracted to both sexes [ant: heterosexual,
           homosexual]
    2: having an ambiguous sexual identity [syn: bisexual,
       epicene]
    n 1: a person who is sexually attracted to both sexes [syn:
         bisexual, bisexual person]

Moby Thesaurus II by Grady Ward, 1.0:

61 Moby Thesaurus words for "bisexual":
   AC-DC, amphierotic, androgyne, androgynous, auntie, autoerotic,
   bi-guy, biaxial, bicameral, bicuspid, bifid, biform, binocular,
   binomial, binominal, bipartite, biped, bipetalous, bipinnate,
   bisexed, bivalent, bull dyke, butch, catamite, chicken, deviant,
   dyke, effeminate, fag, faggot, fairy, femme, flit, fricatrice,
   fruit, gay, gunsel, hermaphrodite, hermaphroditic, homo,
   homoerotic, homophile, homosexual, homosexualist, invert, lesbian,
   mannish, nance, pansy, pathic, perverted, punk, queen, queer,
   sapphic, sapphist, swinging both ways, transvestite, tribade,
   tribadistic, unibivalent